Individuals who can change between top/dominant and bottom/submissive roles—whether from relationship to relationship or within a given relationship—are known as switches, though the term switch in this context is occasionally seen as derogatory and is rejected by many who might simplistically fit the definition. First found in softcore movies and erotic thrillers, depictions of lesbianism entered mainstream cinema in the 1980s. It may also involve porn milf touching, rubbing, or pinching the nipples or other erogenous zones while masturbating. The interaction between tops and bottoms—where physical or mental control of the bottom is surrendered to the top—is sometimes known as power exchange, whether in the context of an encounter or a relationship. But starting with The World Biggest Gangbang , starring Annabel Chong, the pornographic industry began producing a series of films ostensibly setting gangbang records for most consecutive sex acts by one person in a short period. Some couples use pornography at times for variety and to create a sexual interest or as part of foreplay. Guro or Gore is a genre of Japanese pornography involving blood, gore, disfiguration, violence, mutilation, urine, enemas, or feces. It may be used as foreplay, or as an alternative to sexual penetration. Interracial pornography typically employs ethnic and racial stereotypes in its depiction of performers and many of interracial pornographic films still include racial stereotypes, although the segregation of actors by race has diminished considerably. The higher pay scale and profile within gay twinks a production often leads to group scenes where a straight actor only tops. Buck Angel is the best-known actor in this genre. Pornographic films are generally classified into sub-genres which describe the sexual fantasy which the film and actors attempt to create. RACK may be seen as focusing gay hentai primarily upon awareness and informed consent, rather than accepted safe practices. Erotic spanking is the act of spanking another person for the sexual arousal or gratification of either or both parties.